This disclosure relates to underwater charging apparatus having multiple reserve battery modules to provide power in remotely accessible applications, and to their use. One example of such an application is to provide power (for example, backup power) for a subsea electrical power function such as in remote littoral zones where electrical power is needed for many purposes such as replenishing power via direct current to underwater craft (manned and unmanned, including military applications.)
Due to the energy needs required in subsea conditions for charging underwater vehicles, battery choice becomes a key factor. Over time, primary batteries degrade causing a decrease in the batteries' ability to hold a charge and to deliver the charge to a load. Due to the primary battery's state of activation, the battery will lose efficacy as the battery ages. Similarly, rechargeable batteries degrade over time. While rechargeable batteries have the ability to be recharged, these batteries lose their ability to hold the same amount of original charge as the battery ages and/or is used. Further, rechargeable batteries require knowledge that the battery needs to be recharged as well as the time/ability to recharge the battery. The invention is applicable to any electrical power function requiring the use of a battery that may degrade over time.
Due to the harsh environments encountered in subsea (including deepwater) applications such as salt water and high external pressure, subsea critical power applications require an electrical power source capable of ultrahigh reliability and ultralow maintenance and ease of remote replacement without bringing the device to the surface.
To increase the operational ranges and durations of underwater vehicles between charges, particularly those performing critical work or ones operating in remote or dangerous areas, it is desirable to have the ability to install underwater charging stations that effectively extend the vehicles' operability. This also optimizes vehicle battery life while enhancing overall vehicle efficiency and safety.
In view of the above, it is desirable to provide an electrical power source for diverse applications utilizing a plurality of reserve batteries that are easily and remotely replaceable.